We present an advanced method to tailor the optical and electrical properties of semiconductor quantum dot structures. By embedding vertically stacked quantum dots in a two-dimensional superlattice, the advantages of self-organized growth and of band structure engineering can be combined. The transition energies between the dot levels and the extended states of the superlattice can be adjusted by the period of the superlattice. We apply this scheme for photodetectors made of InAs quantum dots embedded in an AlAs/GaAs superlattice. The dark current of these devices is reduced by more than one order of magnitude compared to the devices without a superlattice.

A study of the mechanisms underlying the origin of near-band-edge photoreQectance (PR) in CdTe is reported. We And that multiple transitions, including excitons, must be considered to correctly interpret PR signals at 80 and 296 K near the Eo energy in CdTe. Spectra were measured for both undoped and iodine-doped n-type CdTe. Comparisons with photoluminescence recombination energies and line shapes are made. Free exciton and donor-related transitions dominate the PR signal from CdTe at 80 K, while the 296-K PR spectra is primarily excitooic in nature, even in the n-type material.

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Through the Circular Economy Package, the EU aims to reduce material imports and environmental impacts of waste management. Ambitious recycling targets should help to achieve these objectives. As a response, the waste industry developed technical and organizational solutions that can intervene at different stages of a waste management system in order to increase the recovery of recycling materials, starting with improved separate collection over the use of modern material recovery facilities up to the enhanced treatment of waste incineration ashes. The large question is how each of these options can contribute to increase recycling rates to achieve a circular economy. By reviewing case studies as presented in the most recent literature published since the year 2010 from European countries on the recycling of post-consumer packaging waste of glass, metals, paper, and plastics, this study contributes to answer this question. In the first stage, the review found 644 articles matching with the search terms and published since the year 2010. Of these, 46 remained for an in-depth analysis, since 319 did not present case studies as defined in the scope of this article. The articles reviewed provide a good overview on the state of knowledge on increasing recycling of post-consumer packaging waste by improved separate collection, material recovery facilities, and waste incineration bottom ash treatment. Additional information and case studies, however, are required, particularly large-scale experiments to test new separate collection systems, large-scale with different feedstock material at the most-modern material recovery facilities and waste incineration bottom ash treatment plants.